High temperature components for use in turbine applications and the like, such as aircraft engine applications, watercraft engine applications (both marine and fresh water), and land-based power generation applications, are typically manufactured from nickel (Ni)-based superalloys, iron (Fe)-based superalloys, and/or cobalt (Co)-based superalloys. Although these superalloys demonstrate a useful combination of mechanical properties at moderate temperatures, they do not demonstrate a useful combination of mechanical properties at the ever-increasing operating temperatures required to improve overall turbine performance and efficiency.
In order to overcome the temperature limitations associated with the Ni-based superalloys, the Fe-based superalloys, and the Co-based superalloys, niobium (Nb)-based refractory metal-intermetallic composites (Nb-based RMICs), such as Nb-silicide (Nb—Si) alloys and the like, have been developed. These Nb—Si alloys incorporate a relatively ductile metal phase and a relatively brittle intermetallic phase, providing a useful combination of mechanical properties over a wide range of temperatures, including low-temperature toughness and high-temperature strength and creep resistance.
The Nb—Si alloys, however, present several important manufacturing challenges. The Nb—Si alloys are typically manufactured using conventional ingot metallurgy/thermo-mechanical forming techniques, casting techniques, directional solidification techniques, and/or vapor deposition techniques. The ingot metallurgy/thermo-mechanical forming techniques, for example, suffer from the problem that the Nb—Si alloys must be extruded at temperatures of between about 1,450 degrees C. and about 1,650 degrees C., with only nominal incremental cross-sectional reductions being possible. Likewise, the casting techniques suffer from the problem that the complex chemistries and high reactivities of the Nb—Si alloys make suitable microstructural control difficult to achieve and often result in unwanted flaws. In general, the conventional techniques for manufacturing Nb—Si alloys suffer from compositional inhomogeneities, microstructural inhomogeneities, insufficient size and scale problems, and the inability to form near-net shapes.
Thus, what is needed is an improved method for manufacturing (processing and/or forming) Nb-based RMICs whereby suitable compositional and microstructural control is achieved and complex component geometries of sufficient size and scale may be formed at relatively low temperatures without the need for time-consuming, expensive post-process machining.